Staple fiber blend



Nov. 17, 1964 R. E. KITSON ETAL 3,157,021

STAPLE FIBER BLEND Filed March 1. 1961 INVENTORS ROBERT E. KITSON CEClL. E. REESE ATTORNEY United States Patent 3,157,621 STAPLE FIBER BLEND Robert E. Kitson and Cecil E. Reese, Kinston, N.C., assignors to E. I. du Pont de Nemours and Company, Wilmington, Deb, a corporation of Delaware Filed Mar. 1, 1961, Ser. No. 92,515 Claims. (Cl. 57-140) This invention relates to novel fabrics prepared from staple yarns. More specifically, it is concerned with a novel high bulk fabric and the staple yarn and the tow from which it is prepared.

The preparation of bulky fabrics from staple yarns composed of a blend of high shrinkage and low shrinkage fibers has been previously described. In employing staple yarns of this type, a primary advantage desired for exploitation is development of bulkiness in the fabric during finishing steps subsequent to the Weaving or knitting of the fabric, thus avoiding the problems encountered in processing a bulky yarn such as snagging of the yarn, loss of bulk resulting from tension placed on the yarn, etc. However, the success in obtaining bulky fabrics from high shrinkage/ low shrinkage staple blend yarns has not been as complete as might have been predicted. Although the staple yarns themselves become quite bulky when relaxed in skein form, the bulkiness of the finished fabric is frequently somewhat disappointing, especially when the initial fabric is of dense construction. This phenomenon apparently results from the fact that the fibers which have a nominal high shrinkage usually also have a relatively low yield point, so that they simply tend to yield or llow internally rather than shrink against the constraint afforded by the fabric construction.

In the case of fabrics produced from polyester/wool staple blend yarns, an additional, rather surprising disadvantage has been noted. Usually, in such yarns, the wool is the high shrinkage component and a 10W shrinkage, wear-resistant polyester fiber is selected as the other component. It might be expected, then, that the polyester fibers would be forced to the surface of the fabric via shrinkage of the wool component and that the cover fibers of the fabric would be comprised primarily of the wear-resistant polyester fibers. Surprisingly, however, it is found that the cover fibers in such fabrics are com prised primarily of the wool fibers. The same phenomenon is noted to an even more marked degree, of course, when high shrinkage polyester fibers are blended with wool as the low shrinkage component. This phenomenon prevents use of important styling effects achieved by dyeing the wool and the polyester fibers different tones or colors, since any uneven Wear preferentially wears off the wool and after only moderate use the fabric exhibits creases or spots having a different color than the main body of the fabric.

Various other disadvantages have been noted in the use of high shrinkage/low shrinkage staple blend yarns for producing bulky fabrics. The dimensions of the finished fabric are controlled by the final dimensions of the high shrinkage fibers, and reductions in the dimensions of the finished fabrics are regarded in the textile industry as wasteful of loom capacity. Although the high shrinkage fibers become the load-bearing members of the staple yarns, they also tend to be the Weaker fibers in the yarn, as indicated above. Because the actual amount of fabric shrinkage which will be achieved is uncertain in a new constluction, the desired fabric density must he arrived at through experimentation. Finally, fiber shrinkage is accompanied by a corresponding increase in denier, and since this may reach or the production of a finished fabric comprised of staple fibers of relatively fine denier must proceed from starting material staple fibers of quite low denier indeed.

3,l5?,2l Patented Nov. 1?, i364 "ice The present invention contemplates the provision of a fabric which is permanently bulky to a high degree. Another object of the invention is the provision of such a novel fabric in which the bulkiness is imparted during the finishing of the fabric without encountering undue fabric shrinkage. An additional object is to provide a novel staple yarn from which the novel fabric can be Woven or knitted. A further object is to provide a novel tow from which the staple yarn, and ultimately the bulky fabric, may be prepared. Other objects will become apparent from the following description and claims.

In accordance with the present invention, these objects are achieved by providing a fabric comprised of twisted yarn composed of a blend of two groups of staplelength textile fibers, the fibers of one of said groups having the property of bein spontaneously and irreversibly extensible upon heating and the fibers of the other of said groups having a residual shrinkage, upon heating, in the range of 0 to 15%. When heat is applied to finish the-fabric, it becomes bulky to a high degree and has excellent covering power. The finished fabric has an attractive appearance and hand and is highly suitable for garment and other uses. The finished fabrics have a major proportion of the extensible fibers in the blend distributed on the fabric surface. This is indeed surprising, particularly when natural fibers such as wool, which are known to migrate to the surface during milling and fulling, are utilized in the blend.

The textile yarn from which the novel fabric is woven or knitted also comprises an embodiment of the invention. The spontaneous and irreversibly extensible fibers, which comprise from about 20% to about of the blend, are synthetic linear condensation polyester fibers which have an extensibility from about 1% to about 30%. The staple fibers of the other component of the blend may be synthetic or natural fibers having a shrinkability up to 15%.

The invention also comprehends, as a novel filamentary product from which the staple blend yarn and bullcable fabric may be prepared, a tow comprising a multiplicity of crimped, spontaneously and irreversibly extensible continuous filaments composed of a synthetic linear condensation polyester; the length change of the spontaneously and irreversibly extensible filaments avenaging at least about 5% in Water at C. The tow may be a homogeneous tow comprised entirely of spontaneously and irreversibly extensible filaments, or a substantial portion of shrinkable continuous filaments may be added to the tow. The tow should be in crimped form for suitable processability to staple yarn. The crimp may be formed in the tow via a mechanical device such as a stuifer box crimper, or by other methods such as via jet relaxation of the tow during the step of inducing the property of spontaneous and irreversible extensibility in the polyester filaments.

Hitherto, spontaneously and irreversibly extensible filaments have been employed in continuous filament yarns, but the relatively low yield point of such yarns has been regarded as precluding their conversion to staple yarns owing to the high tensions imposed in forming the stable sliver and spinning it into yarn. Experiments confirm that staple ym'n produced from tow having, for example, 2% to 3% spontaneous and irreversible extensibility in Water at 100 C. actually contains relatively few spontaneously extensible fibers even if care is taken in processing the tow to yarn. In accordance with the present invention, however, it has been found that highly useful, postbulkable staple blend yarns are readily prepared from a cirmped polyester tow containing a substantial proportion of spontaneously and irreversibly extensible continuous filaments in which the length change of the spontaneously and irreversibly extensible filaments averages at least about in water at 100 C.

Surprisingly, a staple blend yarn comprising both shrinkable fibers and spontaneously and irreversibly extensible fibers can be prepared from a homogeneous tow comprised solely of spontaneously and irreversibly extensible filaments, without the addition of any other filamentary or fibrous material, simply by processing the tow to staple yarn. This apparently results from at least partial retention of the property of spontaneous and irreversible extensibility in a portion of the fibers accompanied by development of shrinkability in the remainder of the fibers as they are pulled out under the tensions of staple processing, although this statement is not intended to be construed as limiting the invention. Although best results are generally achieved by adjusting process conditions for minimum tension, conventional apparatus may be employed, and the tow may be converted to the staple blend yarn via either a tow-to-top process or by cutting it to staple fibers and processing it to yarn on conventional equipment. If desired, wool or other shrinkable fibers may be blended with the fibers derived from the spontaneously and irreversibly extensible tow in order to increase the proportion of shrinkable fibers in the staple blend yarn; however, the quantity of shrinkable fibers added should be kept low enough that at least about of the fibers in the fabric, prior to finishing, are spontaneously and irreversibly extensible fibers.

For the purposes of the present invention, the boil-off length change of a fiber upon heating is conveniently determined by immersing the fiber in Water at 100 C. for 5 minutes and expressing the change in length of the fiber as a percentage of its length prior to immersion. Spontaneous and irreversible extensibility of the fiber is expressed as a positive percentage value for boil-off length change. A negative percentage value for boil-olf length change correspondingly refers to retraction in the length of the fiber. The term shrinkage, as used herein, refers to a boil-01f length change of negative value; however, numerical values for shrinkage are given without prefixing the minus sign. Fibers which exhibit no change in length when heated are regarded herein as the limiting case in which the shrinkage is zero (0.0%). The differential boil-01f length change, expressed as the algebraic difference between the boil-off length change values of the spontaneously and irreversibly extensible fibers and the shrinkable fibers, should be at least about 3% in accordance with the present invention; preferably, the differential length change is at least about 10%.

Instead of measuring the extensibility or shrinkability of the staple fibers in the yarn in the fabric, the boiloff length change values of the staple fibers in the yarn prior to forming the fabric may be measured, since the changes in yarn properties resulting from the knitting or weaving operations are generally quite small and may be disregarded. If the yarn is twist-set before conversion to fabric, the properties after twist setting are the significant values to determine.

The spontaneously and irreversibly extensible filaments in the novel tow of the invention should have a length change of at least about 5% in Water at 100 C. However, as indicated above, this property does not carry over unchanged to the fabric form. In fact, the response of the individual filaments comprising the spontaneously extensible tow to the variable tension encountered in staple yarn preparation provides a spectrum of extensibility and shrinkability values in the fibers comprising the staple yarn and the fabric produced therefrom, and this phenomenon actually provides the key to the preparation of bulkable fabrics from a single, initially homogeneous tow bundle. The same phenomenon is operative when shrinkable filaments are incorporated in the tow, or when wool or other shrinkable fibers are added, al though the center of the spectrum of boil-elf length changes is displaced towards the shrinkage side. The net properties of the yarns are most conveniently described by determining the boil-off length changes of a representative sample of fibers, determining the proportion of extensible fibers and shrinkable fibers of each type, and calculating separate average values for each type of shrinkable and extensible fiber.

The term tow, as used herein, refers to a large number of continuous, substantially parallel, synthetic filaments without definite twist collected in a loose, ropelike form. In accordance with the present invention, the filaments in the tow should be crimped. Generally speaking, the minimum number of filaments to which the term tow is considered applicable is on the order of about 10 and, while there is no fixed maximum number, tows containing on the order of 10 filaments or even considerably more are encountered. In general, the size of the filaments is in the range of 1 to 10 denier per filament.

The term spontaneous and irreversible extensibility refers to the property whereby a fiber or filament increases permanently in length without tension being applied to the ends of the fiber or filament; i.e., the fiber or filament does not retract to its original length when cooled and dried. As indicated above, the numerical value is calculated as percentage boil-off length increase based on the initial length of the fiber. In accordance with the present invention, the amount of spontaneous and irreversible extensibility exhibited by the fibers in the staple yarn or fabric may be as low as about 1%, but is preferably 2% or more. As described in copending US. application Serial No. 718,114, filed February 28, 1958, in some cases, filaments having an extensibility of about 30% or even higher are known. The preparation of spontaneously and irreversibly extensible synthetic linear condensation polyester filaments is described by Kitson and Reese in US. Patent 2,952,879 and Belgian Patent 566,145.

In accordance with the invention, the shrinkable fibers in the staple yarn or fabric may be any of the various commercially available fibers having an average residual shrinkage in the range of 0 to about 15%; preferably, the residual shrinkage is no more than about 5%. If desired, the shrinkable fibers may be preshrunk, before being blended with the spontaneously and irreversibly extensible fibers, so that the staple blend yarn and the resulting fabric are substantially stable to dimensional change upon heating. Preferred staple fibers which may be used include wool as well as shrinkable staple fibers composed of linear condensation polyesters such as polyethylene 2,6- or 2,7-naphthalenedicarboxylate, poly(diphenylolpropane isophthalate), and the linear terephthalate polyesters such as polyethylene terephthalate, polyethylene terephthalate/isophthalate 15), polyethylene terephthalate/hexahydroterephthalate 10), and poly- (hexahydroxylylene terephthalate). Other shrinkable fibers which may be used include staple fibers of regenerated cellulose, cellulose acetate, polyacrylonitrile, polyhexamethylene adipamide, and polycaprolactam. Such shrinkable fibers are, of course, well known in the art.

The staple fiber blend yarn of the present invention should include significant amounts of each of the two groups of staple fibers. In general, at least about 20% of each of the two groups of fibers should be included in the yarn from which the novel fabric is prepared. The groups need not be homogeneous; for example, the spontaneously and irreversibly extensible fibers may comprise a mixture of fibers having varying extensibilities when heated in C. water. Similarly, the group of shrinkable fibers may comprise a mixture of fibers having various shrinkage values. However, in any case, at least 20% of the fibers in the yarn should comprise a group of spontaneously and irreversibly extensible fibers which exhibit a minimum differential boil-otf length change of at least about 3% with respect to a second group of fibers, comprising at least about 20% of the fibers in the yarn,

having a residual shrinkage in the range of to about 15%.

By synthetic linear condensation polyester is meant a linear polymer comprised of recurring structural units containing, as an integral part of the polymer chain, recurring carbonyloxy groups and having a relative viscosity of at least about 8 in a solution of 11 g. of the polymer in 100 cc. of a mixed solvent composed of 58.8 parts by weight of phenol and 41.2 parts by weight of trichlorophenol. Preferably, at least about 75% of the recurring structural units of the polyester are derived from a glycol containing 2 to 12 carbon atoms and a dicarboxylic acid selected from the group consisting of terephthalic acid and the naphthalenedicarboxylic acids. reacting the dicarboxylic acid or an ester-forming derivative thereof with an excess of a glycol, G(OH) where --G is a divalent organic radical containing from 2 to 12 carbon atoms and attached to the adjacent oxygen atoms by saturated carbon atoms, or an ester-forming derivative of the glycol. Following the preparation of the monomeric ester, poly-condensation is carried out at elevated temperature and reduced pressure with elimination of excess glycol. Examples of suitable glycols include ethylene glycol, diethylene glycol, butylene glycol, decamethylene glycol, and cisor trans-p-hexahydroxylylene glycol. Mixtures of such glycols may suitably be used to form copolyesters, or small amounts, e.g., up to about 25 mol percent, of a higher glycol may be used, such as a polyethylene glycol. The acid component of the polyester preferably consists of at least 75% of terephthalic acid or a naphthalenedicarboxylic acid, especially 2,6-naphthalenedicarboxylic acid or 2,7-naphthalenedicarboxylic acid. Similarly, copolyesters may be formed by replacing up to about 25 mol percent of the terephthalic or naphthalenedicarboxylic acid or derivative thereof with another dicarboxylic acid or ester-forming derivative thereof, such as adipic acid, dimethyl sebacate, isophthalic acid, hexahydroterephthalic acid, or sodium 2,5-dicarbomethoxybenzenesulfonate. The copolyester may also be formed by replacing part of the terephthalic or naphthalenedicarboxylic acid or derivative thereof with a hydroxy acid or derivative thereof, such as p-(Z-hydroxyethyl)benzoic acid or methyl p-(2-hydroxyethoxy)benzoate.

Linear terephthalate or naphthalenedicarboxylate polyesters and copolyesters are especially suitable for use in the present invention since they have high melting points and since their properties are highly adaptable to provide either shrinkable or spontaneously extensible fibers. The spontaneously and irreversibly extensible linear terephthalate or naphthalenedicarboxylate polyester fibers are also adaptable for dyeing under mild conditions without developing their full extensibility. Thus, the fibers are adaptable for stock dyeing or yarn dyeing without removing their potential for elongating upon further heat treatment in fabric form to provide a high degree of bulk.

In general, the advantages of the present invention are realized most fully by heating the staple yarns to bulk them only after they have been Woven or knitted into fabric. However, in some cases, it may be desirable to impart to the staple yarns a certain amount of bulkiness prior to weaving or knitting. For example, it may be desired to dye the staple yarns prior to making the fabric in order to achieve certain patterned effects in the fabric. In such cases, due to the ease of dyeing the spontaneously and irreversibly extensible component, the yarn may be dyed under mild conditions to minimize bulking, after which it may be processed into fabric and a further heating treatment may be given to provide additional fabric bulkiness. As mentioned above, it is also frequently desirable to twist set the staple blend yarn before making The polyesters may be prepared by it into fabric. This treatment also is preferably carried out under relatively mild conditions to minimize bulkmg.

This invention will be further described by reference to the accompanying drawings, in which FIGURE 1 is an enlarged View of a cross section of a fabric exemplifying the present invention, before boiloif, woven from a staple blend yarn prepared from a spontaneously and irreversibly extensible linear condensation polyester tow, and

FIGURE 2 is an enlarged view of a cross section of the fabric of FIGURE 1, after the fabric has been boiled oif.

Referring now to FIGURE 1, which represents a cross section of the novel fabric of the invention prior to boilolf, the cross section is taken parallel to warp yarns 1 with the filling yarns 2 being seen in section. Both the warp and the filling yarns are twisted staple yarns comprised of a blend of shrinkable fibers 3 (shown as solid lines) and spontaneously and irreversibly extensible fibers 4- (shown in outline). As previously described and as further illustrated in the examples, the twisted staple yarns 1 and 2 are suitably prepared by processing a linear condensation polyester tow having a spontaneous and irreversible extensibility of at least about 5% in C. water into staple yarn using conventional apparatus. Prior to boil-off, the fabric has relatively poor cover and loft and exhibits a rather cool hand.

FIGURE 2 illustrates the appearance of the cross section, after boil-01f, of the fabric of FIGURE 1, using the same reference numerals for the fibers and yarns subsequent to boil-off as for the corresponding fibers and yarns prior to boil-off. Slight fabric shrinkage has occurred (reduced distance between the filling yarn ends 2) owing to the shrinkage of fibers 3 which substantially control the final dimensions of the fabric. Fibers i have elongated irreversibly and are thereby disposed outwardly from the yarn bundle in loops, which are seen not only in the warp but in the filling; such loops are S-dimensional, of course, although necessarily indicated as being in the plane of the paper. The boiled-off fabric has good cover and loft and exhibits a warmer and softer hand than before.

The following examples will serve to illustrate the invention further, although they are not intended to be liinitative.

EXAMPLE I In a series of experiments, 55% polyester/45% wool staple blend yarns identified as Yarn A, Yarn B, and Yarn C are spun and woven into twill fabrics. In each case, 62s wool having a boil-off length change of 0.5% is employed. The polyester staple fibers are spontaneously extensible fibers composed of polyethylene terephthalate/S- (sodiumsulfo) -isophthalate 97.5 2.5) having a relative viscosity of 15.5 and containing 0.3% TiO They are prepared by spinning the polymer, using conventional melt spinning apparatus, at 296 C. through 9-mil round orifices at a spinning speed of 1200 yards per minute and forming a tow comprising approximately 4000 filaments. The tow for Yarn A is drawn from a series of feed rolls through a draw zone in which water at 80 C. is sprayed on the tow bundle to a series of draw rolls operating at a peripheral speed of yards per minute at a draw ratio of 3.86X; for Yarn B the spray temperature is 80 C. and the draw ratio is 323x and for Yarn C the corresponding figures are 70 C. and 3.0l respectively. The drawn tow is then passed through a jet tube wherein it is contacted with steam at about 122 C. for an exposure time of 0.195 second (Yarn A), 0.082 second (Yarn B), and 0.082 second (Yarn C), the tow being ejected from the tube under conditions of free relaxation with development of crimp being observed. The tow is then passed through a conventional stuifer box crimper at low operating pressure and cut to staple fibers on a conventional staple cutter.

The polyester fibers cut from the tow are approximately 2.75-inch, 4 denier per filament fibers.

In each case, a blend of polyester and wool fibers is made on a woolen card and spun on the worsted system into a 55 polyester/45% wool staple yarn. For each fabric, the warp yarns are 1/ 24 worsted count 14 turns per inch (t.p.i.) Z twist and the filling yarns are 1/24 worsted count t.p.i. S twist. The fabrics are 2 x 2 right-hand twills woven to a boil-off weight of 6.9:01 oz./sq. yd. and an end-to-piclr ratio of 52 to 48 after boil-off.

Samples of each of the woven fabrics are immersed for 30 minutes in 5.25% sodium hypochlorite solution at C., a known procedure which dissolves wool fibers without affecting the properties of polyester fibers. individual polyester fibers are then carefully teased out from each of the fabrics and the boil-off length change of each is carefully measured. (It will be noted in the table which follows that the boil-off length change values of the polyester staple fibers have changed considerably from the values observed in the starting material fibers. The wool fibers are all shrin able fibers with an average estimated shrinkage value of 0.5%, as shown in the table.)

The woven fabric is padded with enzyme solution and scoured at 82 C. for 1 hour to remove sizing. The fabric is then beck-dyed with 4% (on weight of wool) of Pontachrome Black TA dye (CI. 14645) and afterchromed with 0.5 g./l. sodium bichromate at 98 C. for a total of 3 hours; only the wool component is dyed. The fabric is then treated with a solution of 5 g./l. of o-phenylphenol solution at 98 C. for 1.5 hours to simulate dyeing of the polyester component of the fabric. The fabric is then dried at 220 C. for 1 minute, nappcd (face only), fulled for 2 hours in a small mill at 50 C., scoured for minutes at 70 C., dried at 220 C. for 1 minute, napped again (face only), sheared, and semidecated.

Samples of each of the fabrics are then shaved, using an ordinary, commercially available mens electric razor on a fixed area of fabric, and the clippings are carefully collected. The clippings in each case are then carefully weighed, treated with 5.25% sodium hypochlorite solution at 25 C. for 30 minutes, Washed with water, dried, and reweighed. The percentage of polyester fibers found in these clippings representing the cover fibers of the fabric are reported in the table as polyester fibers in fabric cover.

The bulk, or specific volume, of each of the fabrics is determined by dividing the volume of the finished fabric by its weight; the volume of a fabric sample of known area being determined by multiplying the area by the thickness measured under a pressure of 3.4 p.s.i. in accordance with Method D76-53 of the A.S.T.M. standards on Textile Materials.

The Streakmeter rating is a measure of surface cover in worsted fabrics determined by a method involving the relative reflectance of light from the twill line and the interstices in an unbroken twill fabric. For this purpose the fabric is mounted on a rotating drum with the twill lines parallel to the axis of rotation. A beam of light is directed along this twill line in an incident angle 45 to the normal. The reflected light passes through a .01 x .50 in. slit and activates a photoelectric cell. Changes in intensity of the reflected light as the fabric is moved are recorded. The record shows a series of deflection representing individual twill lines which are counted electronically. The aggregate amplitude of these deflections (a) divided by the number of twill lines (1) determines the average deflection per twill. This value (a/ t) is characteristic of the degree of weave obscurity achieved and thus a measure of surface cover.

In interpreting results achieved by this rating, high numbers represent relatively poor cover and lower numbers indicate better cover.

The results of the foregoing experiments are recorded in the following table:

Table POLYESTER/WOOL (55%/45%) STAPLE BLEND FABRICS FIBER, YARN, AND FABRIC PROPERTIES Yarn A Yarn B Yam 0 1. Plropcrties of Fibers Cut From Polyester ow: Tenacity, g.p.d 3. 1 2. 6 1.6 Break Elong-rti Pcrccnt: 48 S6 Modulus, g.p.d 21 23 14 Boil-oil length change, percent (average). +0. 5 +5.9 +128 2. Properties of Staple Fibers Removed From Woven Fabric: A. Boil-oil length change 01' extensible polyester fibers, percent (average)..- +0.4 +3 +3.4 Percent Extensible Polyester Fibers 15 30 B. Boil-oil length change of shrinkable polyester fibers, percent (avorage) 2 2. 5 Percent Shrinkable Polyester Fibers 40 25 0 O. Boil-oil length change of wool fibers,

erccnt (average) O. 5 O. 5 O. 5 Percent Wool Fibers 45 45 45 3. Polyester Fibers in Fabric Cover, Percent" 30 41 45 4. Properties of Finished Fabrics:

Bulk, cc./g 2. 2 2. 3 2. 6 Streakinotor Rating 38. 0 24. 9 23. 0

An attractive fabric similar to that obtained from Yarn C is obtained by repeating the preparation of Yarn C with the omission of the stuifer box crimping step and weaving and finishing a fabric as described above, relying in this case solely on the crimp developed in the tow upon passage through the steam jet.

Example 11 A polyester tow is prepared as described in Example I, employing 66 C. spray and a draw ratio of 2.78X, the draw speed being 159 y.p.m. The drawn tow is relaxed 57.5% in a steam tube at C. with an exposure time of 0.15 second, after which it is passed through a conventional stuffer box crimper at low operating pressure. The tow comprises approximately 16,000 filaments having a drawn denier per filament of 4.5. The filaments have a tenacity of 1.1 g.p.d., a break elongation of 102%, a yield point of 0.45 g.p.d., a modulus of 7.8 g.p.d., and a boil-off length change of +10.5%.

The tow is converted to top using a Pacific type tow-to-top converter with a 3 /2 inch variable cut. Wool top derived from 64-70s wool is blended with the polyester staple fibers on a pin drafter and the blended top is spun on the Worsted system into l/ 24 worsted count 55% polyester/45% wool staple yarn. The yarn is twisted to 14 t.p.i. S twist for the warp and 10 t.p.i. Z twist for the filling and twist-set at 82 C. for 60 minutes. 2 x 2 right-hand twill fabrics are woven to a finished count of 74 ends x 71 picks and a finished weight of 8.02 02/ sq. yd. The fibers comprising the gray fabric are analyzed as in Example I, and it is ascertained that the fabric comprises 25% spontaneously and irreversibly extensible polyester fibers having an average boil-off length change of +5%, 30% shrinkable polyester fibers having an average boil-off length change of 3.5%, and 45% wool fibers having an average boil-off length change of 0.5%.

The gray fabric is divided into a series of test fabrics which are then finished in different ways to test the effect of some of the finishing steps on fabric bulk. The complete finishing sequence for these fabrics comprises a series of steps of the type described more fully in Example I including desizing, scouring, drying, dyeing of the wool component, simulated dyeing of the polyester component, fulling, scouring, drying, brushing, shearing, semi-decating, and a final heat-setting treatment at 200 C. for 5 minutes under tension to maintain constant fabric area. Test Fabric E is given the complete finishing sequence. Test Fabric D is finished according to the sequence but with the fulling step omitted; Test Fabric C is given the complete sequence except that the final heat setting step is omitted; and Test Fabric B is given the finishing sequence with both the fulling and heatsetting steps omitted.

A conventional fabric, identified as Control Fabric A, is also prepared by repeating the procedure described above to make a 55% polyester/45% wool staple blend yarn, weaving it to a twill fabric of the same construction, and giving it the same complete finishing sequence, the only variation in the procedure being substitution of the spontaneously and irreversibly extensible polyester tow starting material with a conventional shrinkable crimped tow comprised of the same polymeric material and having a tenacity of 3.2 g.p.d., a break elongation of 45%, a modulus of 35 g.p.d., anda boil-off length change of 0.3%. 1

The bulk of each of the various fabrics prepared as described above is then determined. The results are shown in the following table:

Bulk, cc./ g.

Control Fabric A-complete finishing sequence 2.26

Test Fabric Bfulling and heat setting omitted 2.33

' Test Fabric C-heat setting omitted 2.43

Test Fabric D-fulling omitted 2.58

Test Fabric Ecomplete finishing sequence 2.73

EXAMPLE III A polyester tow comprising 5,000 filaments and having an undrawn denier of approximately 33,000 is melt spun as described in Example I. The tow is drawn 2.96 through a 73 C. aqueous spray at a draw speed of 70 yards per minute, passed through a slot wherein it is contacted with a jet of steam at about 120 C. for an exposure time of 0.105 second and ejected under conditions of free relaxation, crimped in a conventional stuffer box crimper under low operating pressure, and finally cut to 2.5-inch staple fibers. The fibers have a denier per filament of 3.1, a tenacity of 1.8 g.p.d., an initial modulus of 29 g.p.d., a break elongation of 116%, a yield point of 0.7 g.p.d., and a boil-off length change of +16%.

Another polyester tow is prepared in similar fashion, except that the polymer contains 2% carbon black; in this case, the draw ratio is 3.49 the draw speed is 74 yards per minute, and the exposure time of the tow in the steam jet is 0.110 second. The 2.5-inch staple fibers have a denier per filament of 3.4, a tenacity of 1.7 g.p.d., an initial modulus of 31 g.p.d., a break elongation of 101%, a yield point of 0.6 g.p.d., and a boil-off length change of Equal weights of the black and white polyester staple fibers are blended on a woolen card and spun on the worsted system to prepare warp yarns of 1/ 22.5 worsted count, 12.5 t.p.i. Z twist and filling yarns of 1/22.5, 10.0 t.p.i. S twist. A 2 x 2 right-hand twill fabric is woven from this yarn to a boil-off weight of 6.9102 oz./sq. yd. and an end to pick ratio of 55 to 45.

Individual polyester fibers are carefully teased out from samples of the yarn used to weave the fabric and the boil-off length change of numerous of the black and white fibers removed from the yarn are measured. It is observed that about one-quarter of the black fibers are spontaneously elongatable, having an average length change of +49%, and three-quarters are shrinkable with an average change of 11.2%. The white fibers have similar properties, about one-quarter being elongatable with a length change of +48% and the remaining threequarters having an average length change of -1l.7%.

The gray fabric is finished in a sequence of steps of the type described more fully in Example I including desizing, scouring, napping, fulling, scouring, drying, heatsetting, brushing, shearing, and. semi-decating. The finished fabric has a bulk of 3.13 cc./ g. (weight of fabric 6.7 oz./sq. yd.) as compared with a bulk of only 1.96 cc./g. (weight of fabric 6.8 oz./sq. yd.) for a conventional fabric prepared in the same way from a conventional shrinkable crimped tow comprised of the same 7 1o polymeric material and having a tenacity of 3.2 g.p.d., a break elongation of 45%, a modulus of 35 g.p.d., and a boil-off length-change of -0.3%.

EXAMPLE IV Polyethylene terephthalate/S-(sodium sulfo) isophthalate (97.5/25) having a relative viscosity of 13.5 and containing 0.3% TiO is spun at 295 C. from conventional melt spinning apparatus through a spinneret plate containing pairs of orifices 7 and 6 mils in diameter separated by a 2-rnil web to form filaments having a pear-shaped cross section via coalescence of the extruded polymer streams from adjacent orifices. The spinning speed is 1200 yards per minute. A tow comprising 9600 filaments isformed and passed from a prewetting bath at 32 C., through a series of feed rolls, through a draw zone in which water at 72 C. is sprayed on the tow bundle, and thence to a series of draw rolls operating at a peripheral speed of 100 yards per minute, the draw ratio being 3.3 X. The drawn tow is passed through a slot wherein it is contacted with a jet of steam at 124 C. for an exposure time of 0.2 second and ejected under conditions of free relaxation, crimped in a conventional stuifer box crimper under low operating pressure, and finally cut to 3-inch staple fibers. The fibers have a denier per filament of 3.9, a tenacity of 1.8 g.p.d., an initial modulus of 14 g.p.d., a break elongation of 103%, a yield point of 0.5 g.p.d., and a boil-off length change of +12.6%.

The spontaneously and irreversibly extensible staple fibers prepared as described above are blended in a 4 to 1 ratio on a pin drafter with conventinal crimped staple fibers comprised of the same polymeric material having a tenacity of 3.2 g.p.d., a break elongation of 45 a modulus of 35 g.p.d., and a boil-off length change of 0.3%. The fiber blend is spun on the woolen system to form a 2/5 wool run 102/48 twist yarn. Individual polyester fibers are carefully teased out from samples of the yarn and the boil-off length change of numerous of the fibers are measured. It is observed that about half of the fibers are spontaneously elongatable, having an average length change of -{3%, and half are shrinkable, with an average length change of 1%.

The yarn is then knitted on a 12 cut Jacquard knitting machine in a Jersey stitch at 12 courses per inch. The knit fabric is dyed with 2%, based on fabric weight, of 1,4 diamino 2,3 dichloroanthraquinone at 100 C. for 1.5 hours, whereupon it is dyed a deep shade of violet. The resulting fabric has a weight of 9.59 oz./yd. a thickness of 0.043 inch, and a bulk of 3.36 cc./g.

When yarn is prepared solely from the conventional crimped staple fibers and is knitted to the same fabric construction, the resulting fabric dyes only to a light shade of violet and has only 85% of the bulk of the test item.

As many widely different embodiments of this invention may be made without departing from the spirit and scope thereof, it is to be understood that this invention is not to be limited to the specific embodiments thereof except as defined in the appended claims.

We claim:

1. A textile yarn comprised of from about 20% to about of staple-length fibers of a synthetic linear condensation polyester, which fibers in response to boiling in Water for five minutes exhibit extension of at least 1%, and from about 80% to 20% of shrinkable staplelength fibers, which fibers in response to boiling in water for five minutes shrink up to 15%, said extensible fibers and said shrinkable fibers exhibiting a differential change in length of at least 3% when immersed in boiling water for five minutes.

2. The yarn of claim 1 wherein said shrinkable fibers are synthetic fibers.

I 3. The yarn of claim 1 wherein said shrinkable fibers are wool fibers.

4. The yarn of claim 1 wherein said shrinkable fibers have a shrinkability of not more than about and said differential change in length is between about 3% and 5. A textile fabric comprised of twisted yarns of a blend of staple-length fibers, said blend being comprised of from about 20% to about 80% synthetic linear condensation polyester fibers which in response to boiling in water for five minutes exhibit extension of at least 1%, and from about 80% to 20% of shrinkable fibers having a shrinkability of up to in response to boiling in water for five minutes, said extensible fibers and said shrinkable fibers exhibiting a differential change in length of at least 3% when immersed in boiling water for five minutes.

6. The fabric of claim 5 wherein said fibers exhibit a differential change in length between about 3% and 10%.

7. The fabric of claim 6 wherein said shrinkable fibers are synthetic fibers.

S. A bulky, fulled fabric composed of twisted yarns of a blend of staple-length fibers, said blend being composed of from about to 80% synthetic linear condensation polyester fibers which in response to boiling in water for five minutes exhibit extension from 1% to 10% and from about 80% to 20% of shrinkable fibers having a shrinkability of up to 5% in response to boiling in water for five minutes, said polyester fibers and said shrinkable fibers exhibiting a differential change in length 12 between about 3% and 10% when immersed in boiling Water for five minutes, said fabric having distributed on its surface a major proportion of the extensible fibers in said blend.

9. The fabric of claim 8 wherein said shrinkable fibers are wool fibers.

10. A textile blend of staple length fibers prepared from a tow comprised of crimped, spontaneously and irreversibly extensible continuous filaments composed of a synthetic linear condensation polyester, the length change of the spontaneously and irreversibly extensible filaments averaging at least about 5%, comprised of from about 20% to about 80% of extensible staple fibers exhibiting an extension of from about 1% to about and the remainder of said blend comprised of shrinkable staple fibers having a shrinkability of up to 15% in response to boiling in water for five minutes, said extensible fibers and said shrinkable fibers exhibiting a differential change in length of at least 3% when immersed in boiling water for five minutes.

References Cited in the file of this patent UNITED STATES PATENTS 2,979,883 Waltz Apr. 18, 1961 OTHER REFERENCES Press, Man-Made Textile Encyclopedia 1959, Textile Book Publishers, Inc., New York (p. 575 only). 

5. A TEXTILE FABRIC COMPRISED OF TWISTED YARNS OF A BLEND OF STAPLE-LENGTH FIBERS, SAID BLEND BEING COMPRISED OF FROM ABOUT 20% TO ABOUT 80% SYNTHETIC LINEAR CONDENSATION POLYSTER FIBERS WHICH IN RESPONSE TO BOILING IN WATER FOR FIVE MINUTES EXHIBIT EXTENSION OF AT LEAST 1%, AND FROM ABOUT 80% TO 20% OF SHRINKABLE FIBERS HAVING A SHRINKABILITY OF UP TO 15% IN RESPONSE TO BOILING IN WATER FOR FIVE MINUTES, SAID EXTENSIBLE FIBERS AND SAID SHRINKABLE FIVERS EXHIBITING A DIFERENTIAL CHANGE IN LENGTH OF AT LEAST 3% WHEN IMMERSED IN BOILING WATER FOR FIVE MINUTES.
 10. A TEXTILE BLEND OF STAPLE LENGTH FIBERS PREPARED FROM A TOW COMPRISED OF CRIMPED, SPONTANEOUSLY AND IRREVERSIBLY EXTENSIBLE CONTINOUS FILAMENTS COMPOSED OF A SYNTHETIC LINEAR CONDENSATION POLYSTER, THE LENGTH CHANGE OF THE SPONTANEOUSLY AND IRREVERSIBLY EXTENSIBLE FILAMENTS AVERAGING AT LEAST ABOUT 5%, COMPRISED OF FROM ABOUT 20% TO ABOUT 80% OF EXTENSIBLE STAPLE FIBERS EXHIBITING AN EXTENSION OF FROM ABOUT 1% TO ABOUT 30% AND THE REMAINDER OF SAID BLEND COMPRISED OF SHRINKABLE STAPLE FIBERS HAVING A SHRINKABILITY OF UP TO 15% IN RESPONSE TO BOILING IN WATER FOR FIVE MINUTES, SAID EXTENSIBLE FIBERS AND SAID SHRINKABLE FIBERS EXHIBITING A DIFFERENTIAL CHANGE IN LENGTH OF AT LEAST 3% WHEN IMMERSED IN BOILING WATER FOR FIVE MINUTES. 